Fuel-air control mechanism for metering flow of fuel to afterburners in jet or turbine engines



Sept. 4, 1956 A. s. ATKINSON 2,761,230

FUEL-AIR CONTROL MECHANISM FOR METERING FLOW OF FUEL TO AFTERBURNERS IN JET OR TURBINE ENGINES Filed Aug. 31, 1950 H 4, E I

.FROM

FUEL TANK r 3mm ,K a ALLEN S. ATKINSON /2 46 #4 United States Patent Application August 31, 1950, Serial No. 1 812,527 A Cl ims- (C 6) (Granted under Title 35, "II-S. Code (1952), see. 266) The present invention relates to fuel metering devices generally and to a fuel metering means for a turbine or j engine af erhuru r sp cifical y- Control mechanisms for metering the flow .of fuel to afterburners in jet or turbine engines ,now in use are of two types, those having manual control and those with thermostatic control. In the former, as is obvious, the rate ,of fuel flow to an afterburner is regulated by the pilot or engineer to provide for the amount of .augmen ted thrust desired and attainable with theafterburner. In the latter type of control, the temperature .of the gases in the turbine outlet is generally used to vary'the rate .of flow of fuel to the afterburner ,in order that .the temperature at the turbine outlet be kept constant. ,In such a type of control variations in pressure due to altitude are a ly comp n a e for by measur ng t e t perature of the compressor discharge and controlling air flow through an airadriven fuel pump to regulate the fuel fl w t the ft rbume The disadvantages of these present control systems .are n me u The re p ns o .a t mperature change .in the turbine outlet isslow; electrical systems necessary to sense the temperature are complicated and expensive; .and the p rforma c f an al itude compensator is freq ent1vp whe bjec to t e change in ambient tempe a as We l as cha e in pr ssure.

It is an object, therefore, of this invention to provide a fuel flow metering device for .an .afiterburner which is simple in construction and reliable in operation.

Another object of the invention is to provide a fuel metering device for an afterburner which ;is not subject nor responsive to the high temperatures of the exhaust gases.

A furtherobject .is .to provide a fuel =fiow control which may be adjusted without affecting. 'the-efiiciency of the engine cycle.

A still further .object is to provide a fuel flow control which is fast and responsive to the rapid changes in altitude or ambient air pressures encountered by rapidly ascending aircraft, guided missiles or jet propelled supersonic. weapons.

The exact nature of this invention as well as other objects and advantages thereof will be readily apparent from considerationof the following specification relating to the annexed drawing in which:

Fig. 1 is a schematic diagram of the components of the invention;

Fig. 2 is a detail view showing the pressure sensory pipes placed at the intermediate compressor stage of the engine; and, i

Fig. 3 is a detail view showing the pressure sensory pipes placed in the turbine stage of the engine.

Referring to the drawing, which is more or less schematic in form, the jet engine body is shown as having a rotor 11 with compressor blades 12 and turbine blades 13. In the jet nozzle 14 is shown the afterburner nozzle ring with nozzles 15. Fuel is supplied from a fuel tank :the afterburner nozzles 15.

.finot shown) to the fuel pump 16 andunder-pressure t0 the chamber '17 in the housing "18 which :has imetering orifice 19 in wall-20 opening :into pipe 20' leading to Metering orifice :19 has a needle valve 21 on stem 22 :slidably supported in ithe ihousing 18.by.sleeve 23. A- diaphragm 24 :separateschamber 17 froma second chamber27 fin thetadjacentrhousing 25; and a second'diaphragm 26divides thedattenhousing into two chambers-27 and 28. An auxiliary chamber diaphragm -30 to which theustemt 22 of valve 21 is fixed. The valve .251 is biased =into-tseating position by spring 31. Chamber 29isconnectedtbytthe pipe 32 to the fuelpump pressure lineito provide-thelsame pressure as in chamber '17. Diaphragms 24 .and;26 ;are sealed to stem 22 and move -.it,.in a qconventionalsmanner, tto open -or close metering orifice :19. ,A fuel gpumpsout- .put vpressure regulating device 1 .33 is r connected -.to ipressure line 34and has a valve 35lheldnormally closedtbyispring 36, the tensiongof whichislmadeladjustable byithe movable :springseat 37 and;adjustable-screw 38.

.Still another .-dia,phragm :39 compartments ithe spring 36 with therelief {passage s401allowing movement of dia- -phragm.39 .Fuel fiowthroughvalve 35-is led back totthe fuel pump 16.through-,by1pass41.

Chambers 27 and 28 are connectedtby pipest42 and 43, respectively, to the vicinity .-of the compressor discharge region, pipe 42, .as shown in Fig. :1, having an inletopening directed-upstreamin.theimmediateldischarge region of the last cornpressor stage and pipe 4-3 lhaving an inlet opening in. the same region directed .transversely to the airstream. Thus, it is seen that chamber .27 is fed with the total impact air pressure of the regionaand chamber v28 with the static .air pressure, {the difference between the impact air pressures-and {the static air pressure being the differential pressure (AP-)m in "the equation .where Wa=the .mass .flow .of air through the turbo-jet ngine, K=..a.c.onstant dependent .upon the-dimensions of the particular .turboflet engine, .and vN= the rotational speed of .the turbo-jet engine compressor .or impeller. This basic relation asset forth in .the above equation .has been previously disclosed by D. G. .Russ .in S..'Patent #2441377 issuedMayQS, .1948. .Forzaparticular engine, assuming N to beatconstantR. P. .M., oroptimum speed, then .the mass flow ofair through .the.engineisproportional to the pressure differential, and with the present invention in use, the rate .-.of How. of fuel .to .theafterburneris therefore proportional .to or .a function of .the,mass..air flow.

Inoperation, the .itnpactairpressure in .pipeAZ .tends to move the diaphragm .26.towar.d the left lifting the needle valve 21 from its :seat .and permitting fuel .flow to the afterburner nozzle .15. l-Pressuredrop in the .fuel through orifice 19 is maintained substantially constant for :any degree of opening due to the control exertedbythe fuel .pumps output regulating device 33. The force tending to move the needle valve 21 .to the left is the. product .of the dilference between the p essures .on opposite sides of the diaphragm 26 and the effective area of the diaphragm 26. The spring 31 exerts a force upon the valve stem 22 to the right which is the product of the spring constant and the displacement to the left of the valve stem, therefore needle valve 21 is contoured so that the area of opening through the orifice 19 is proportional to or a predetermined function of the movement to the left of the needle valve 21. As will be readily seen, the areas of the diaphragms 24 and 30 are substantially equal and as each of chambers 17 and 29 are under the same fuel pressure in the fuel of the valve stem 22 in either direction is not impeded pressure line 34, the movement by the forces on the diaphragms 24 and 30, and is still the result of the difference between the pressure in chambers 27 and 28. The adjustment of the fuel pressure at the jet nozzles 15 is made by varying the resistance of spring 36 by adjustment of screw 38 thus varying the fuel-air ratio to obtain optimum performance of the afterburner.

It should be understood, of course, that the foregoing disclosure relates to only a preferred embodiment of the invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims. For example, although the end portions of pipes 43 and 42 are located in the immediate discharge region of the last stage of the axial compressor in the figure they may be located at the immediate discharge of any stage of the compressor or at the discharge of the turbine, as shown in Figs. 2 and 3, respectively. In these figures pipes 44 and 45 correspond to the total pressure pipe 42 of Fig. l and pipes 46 and 47 to the static pressure pipes of Fig. 1. Also, the compressor may be of the centrifugal or of the mixed flow type, or may be any other type of rotor which handles all of the flow of any single fluid through the engine as for example an air turbine in a ram jet engine which drives engine accessories.

The invention described herein may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of any royalties thereon or therefor.

What is claimed is:

1. In combination with a jet engine having an air compressor in an inlet leading to a combustor and an exhaust nozzle with an afterburner therein, a fuel-air ratio control for the afterburner comprising a body defining four aligned chambers, a flexible diaphragm in said body separating each of said chambers from the chamber adjacent, a first conduit connecting the end two chambers of said four aligned chambers to a source of fuel under pressure, a metering port in said body connecting one of said two end chambers with a second conduit leading to said afterburner, a third and a fourth conduit connected one to each of the inner two of said four aligned chambers and opening into the air inlet of the jet engine immediately aft of said compressor to receive static pressure and total fluid pressure respectively, a valve coacting with said metering port and having its stem secured to each of said diaphragms and operable to open by movement of said diaphragms upon an increase of total fluid pressure over static fluid pressure, fuel pressure regulating means in said first conduit, and spring biased valve closing means in the other of said two end chambers.

2. In combination with a jet engine having a zone of air under pressure immediately aft of the engine compressor, an exhaust nozzle, an afterburner positioned to discharge into said exhaust nozzle, a fuel regulator for the afterburner comprising a body defining two chambers, a diaphragm separating said chambers, a first conduit connecting one of said chambers to said jet engine and opening into said zone of air under pressure to sense static fluidpressure, a second conduit connecting the other of said chambers to said jet engine and opening in said zone to sense total fluid pressure, a fuel conduit connecting said afterburner with a source of fuel under pressure, a metering valve in said fuel conduit, a stem connecting said diaphragm with said valve operable to open said valve in accordance with the air mass flow through said zone upon an increase of total fluid pressure over static fluid pressure as sensed in said first and second conduits, spring means external to said chambers and operatively related to said stem for holding said valve normally in closed position, fuel pressure regulating means connected to said fuel conduit, and means for adjusting the fuelair ratio in said afterburner, the outer wall of said chambers adjoining the fuel conduit being flexible and said stem passing through and being sealed to said wall.

3. In combination with a jet engine having a compressor and burner, a fuel metering device for said jet engine comprising a housing, a first flexible diaphragm dividing said housing into two chambers, a total fluid pressure sensing means in the immediate discharge region of the engine compressor, a static fluid pressure sensing means located adjacent said total pressure sensing means, means connecting each sensing means to a separate one of said chambers, a conduit for conveying fuel under pressure to the jet engine burner, a valve in said conduit, a second flexible diaphragm separating said fuel conduit and the chamber receiving total fluid pressure from said compressor, a stem passing through said second diaphragm and sealed thereto with one end connected to the chamber diaphragm and the other end connected to the fuel conduit valve, and means for balancing the fuel pressure on said second diaphragm.

4. In combination with a jet engine having an air compressor and burner, a fuel metering device for said jet engine comprising a housing, a flexible diaphragm dividing said housing into two chambers, a total fluid pressure sensing means in the discharge region of the engine compressor, a static fluid pressure sensing means located transversely to the air stream in the discharge region of the engine compressor, means connecting each sensing means one to each of said chambers, a conduit for conveying fuel under pressure to the jet engine burner, a valve in said conduit, a stem connecting said valve to said diaphragm operable to open said valve by movement of said diaphragm in accordance with the pressure difference between said chambers, spring means exterior to said chambers and operatively related to said stem for holding said valve normally in closed position, and a second flexible diaphragm separating said fuel conduit and the adjoining one of said two chambers, said stem being sealed to said diaphragm.

References Cited in the file of this patent UNITED STATES PATENTS 1,102,345 Lemale July 7, 1914 2,407,115 Udale Sept. 3, 1946 2,440,663 Ifield Apr. 27, 1948 2,441,948 Atkinson May 25, 1948 2,442,954 Lee June 8, 1948 2,516,147 Robinson July 25, 1950 2,531,780 Mock Nov. 28, 1950 2,545,703 Orr Mar. 20, 1951 2,545,856 Orr Mar. 20, 1951 2,570,591 Price Oct. 9, 1951 2,641,105 Drake June 9, 1953 

